Method of joining two or more substrates with a seam

ABSTRACT

A method for joining two or more substrates with a seam is provided. The seam is formed with a thermoplastic tape that is capable of forming an adhesive bond and a physical bond with a substrate. For instance, in one embodiment, the thermoplastic tape is formed from a polyurethane film. In addition, the seam can be utilized in a flat configuration or folded into a variety of different shapes, such as in a z-shaped configuration. As a result of the present invention, it has been discovered that a seam can be formed to have improved strength without substantially sacrificing the desired functional properties of the substrate materials.

BACKGROUND OF THE INVENTION

[0001] Separate sheets of materials, such as fabrics, have beentraditionally attached together for a variety of purposes using seamsthat were stitched or sewn into the fabrics. However, the stitching ofseams into fabrics can be a relatively slow, expensive process that isundesired in some applications. Moreover, the use of sewn stitches maybe completely undesired for certain types of materials, such as barrierfabrics, that require the seam area to also retain a barrier function.

[0002] Thus, in response to such problems, various other methods forattaching separate fabrics have been developed. For instance, variousthermal methods that rely on the melting behavior of the fabrics havebeen utilized to produce seams. Specifically, the fabric and seam areheated to a certain temperature such that the materials of the fabricand seam begin to melt. Upon melting, thermal bonds are formed at thecrossover points of the melted fabric and seam fibers. Other methodshave also utilized adhesives, such as solvent-based liquid adhesives orglues. However, one problem with these techniques is that the seams aresubject to stress fracture at low temperatures, and even at elevatedtemperatures, the divergent thermal melting points cause the resultingseam to be relatively weak.

[0003] In an attempt to improve strength, some methods have alsoutilized adhesive and/or thermal methods in conjunction with aconventional sewn seam. For instance, one such method includes sewing aseam, such as a lap seam or double-felled needle seam, between twofabrics. Thereafter, one piece of a tape is placed in its entirety onlyon the upper surface of the first fabric, while another piece of tape isplaced in its entirely only on the lower surface of the second fabric.The tapes are then sealed under heat and pressure. Nevertheless, oneproblem with such a process is that it is relatively inefficient andcostly. In particular, during manufacturing, a seam must be first sewninto the substrates and then the tapes are applied. Such multiple tasksadd manufacturing costs and raw material costs. In addition, holes areoften formed in the substrate by the needles during sewing. Although thetape can sometimes seal the needle holes, it is still possible that thefill-in might be incomplete. Unfortunately, the presence of any holes ina substrate can be undesirable for certain applications, such as whenthe substrate is used as a barrier fabric.

[0004] As such, a need currently exists for an improved method offorming a relatively strong seam between two or materials.

SUMMARY OF THE INVENTION

[0005] In accordance with one embodiment of the present invention, amethod of forming a seam between substrates (e.g., fabrics) is provided.For example, the method includes providing a first substrate and asecond substrate. Each substrate has an upper surface and a lowersurface that define at least one edge.

[0006] A first tape portion is placed adjacent to the first substratesuch that the tape portion is placed in operative communication with theupper and lower surfaces of the first substrate. Further, a second tapeportion is placed adjacent to the second substrate such that the secondtape portion is placed in operative communication with the upper andlower surfaces of the second substrate. Each tape portion comprises athermoplastic material that is melt-flowable when subjected to a certainamount of heat and pressure. For example, in one embodiment, the tapecontains polyurethane.

[0007] In addition, the method also includes forming an adhesive bondand a physical bond between the first tape portion and the firstsubstrate and between the second tape portion the second substrate. An“adhesive bond” generally refers to a bond that results from attractiveforces between two or more materials. For instance, adhesive bonds maysometimes result from “dipole-dipole forces” between materials, whichare a type of van der Waals force that occurs upon the interaction ofthe dipole moments of two polar molecules. In addition, a “physicalbond” can refer to the physical intermingling of a material within theinterstices of a substrate.

[0008] In some embodiments, the method can also include heating thefirst tape portion and/or the second tape portion to a certainpredetermined temperature. For example, in some embodiments, the firsttape portion and/or the second tape portion can be heated to atemperature of between about 10° C. below the thermal melting point ofthe thermoplastic material to about 50° C. above the thermoplasticmaterial. Besides being heated, the first and/or second tape portionscan also be subjected to a certain pressure. For example, in someembodiments, the first and/or second tape portions can be subjected to apressure of between about 40 pounds per square inch to about 120 poundsper square inch.

[0009] If desired, the tape portions may also be folded or shaped beforeand/or after being placed adjacent to the first and second substrates.For example, in one embodiment, the tape portions can be folded into az-shaped configuration.

[0010] In accordance with another embodiment of the present invention, aseam is provided that includes a first substrate and a second substrate.Each substrate has an upper surface and a lower surface that defines atleast one edge. In addition, the seam comprises a first tape portion anda second tape portion that are adhesively and physically bonded to thefirst substrate and the second substrate, respectively.

[0011] Other features and aspects of the present invention are discussedin greater detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of one embodiment of a tape that canbe used to form a seam in accordance with the present invention;

[0013]FIG. 2 is a perspective view of one embodiment of a folded tapeused to form a seam in accordance with the present invention;

[0014]FIG. 3 is a perspective view illustrating one embodiment of thepresent invention for forming a seam between two substrates using thetape of FIG. 2;

[0015]FIG. 4 illustrates one embodiment of a seam formed according tothe present invention;

[0016]FIG. 5 illustrates one embodiment of a multi-layered tape usedform a seam in accordance with the present invention; and

[0017]FIG. 6 are SEM photomicrographs of a seam formed according to oneembodiment of the present invention in which FIG. 6A is a seam formed bya polyurethane bilayer thermoplastic tape bonded at 380° F., shown at amagnification of ×100, and FIG. 6B is the seam shown in FIG. 6A at amagnification of ×200.

[0018] Repeat use of reference characters in the present specificationand drawings are intended to represent same or analogous features orelements.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

[0019] It is to be understood by one of ordinary skill in the art thatthe present discussion is a description of exemplary embodiments only,and is not intended as limiting the broader aspects of the presentinvention, which broader aspects are embodied in the exemplaryconstruction.

[0020] In general, the present invention is directed to a method ofjoining two or more substrates with a thermoplastic tape. For example, athermoplastic tape used in the present invention is capable of formingboth an adhesive bond and a physical bond with a substrate. As a result,it has been discovered that the tape can form a seam between twosubstrates that has excellent tensile strength in comparison toconventional seams. In addition, such enhanced tensile strength can beachieved without having a substantial adverse affect on the functionalproperties of the substrates (e.g., barrier properties, etc.).

[0021] A variety of substrates can generally be joined with athermoplastic tape in accordance with the present invention. Forinstance, some substrates that can be utilized include fabrics, such aswoven, knitted, nonwoven fabrics, or composites thereof. When utilized,the fabrics may contain synthetic fibers, natural fibers, or blendsthereof. In addition, other materials may also be utilized, such aselastomeric materials (natural or synthetic), paper-based materials(e.g., natural pulp or a blend of natural and synthetic short fibers),extruded films (e.g., films of thermoplastic or thermoplasticelastomeric polymers), etc.

[0022] The substrates can also have any desired shape, size, orconfiguration. For example, a substrate may be provided as a flat sheetof material having linear and/or nonlinear edges. In some instances, thesubstrates may also have extended lengths and/or substantially parallellongitudinal edges. If desired, the edges of one or more of thesubstrates may be finished by cutting and/or by a selvage. In someembodiments, one or more of surfaces of a substrate may also be coatedor surface-treated with a treatment, such as a silicon treatment, toalter or enhance the surface properties or barrier performance of thematerials. It should be understood that the substrates described aboveare only examples of some substrates that can be utilized, and that thepresent invention is not limited to the use of any particular substrate.

[0023] As mentioned above, a seam can be formed between two or moresubstrates utilizing a thermoplastic tape. In general, any of a varietyof thermoplastic materials can be utilized in the thermoplastic tape ofthe present invention. For instance, some examples of suitablethermoplastic materials that can be used in the present inventioninclude, but are not limited to, polyurethane, polyethylene,polypropylene, copolyesters, and the like. In one embodiment, forexample, the thermoplastic tape is formed from an extruded polyurethanefilm. The thermal melting point of the thermoplastic materials used toform the thermoplastic tape may be the same or different than thematerials used to form the substrate(s). For example, in some instances,the substrate materials have a thermal melting temperature that isgreater than the thermal melting temperature of the tape material(s) sothat the substrate substantially retains its structure and functionalproperties upon the application of heat and pressure.

[0024] In many instances, the tape may also contain more than one typeof thermoplastic material. For example, the tape can be a composite of athermoplastic polymer that is blended or layered with anotherthermoplastic polymer. In one embodiment, for instance, the tapecontains a blend of at least two thermoplastic polymers that havethermal melting points that differ by at least about 5° C. In anotherembodiment, the tape is a layered composite material such that oneportion of the tape is formed from a first thermoplastic polymercomponent, while another portion of the tape is formed from a secondthermoplastic polymer component. For example, up to 75% of the tapewidth can be formed from the first thermoplastic polymer component,while the remainder of the tape width can be formed from the secondthermoplastic polymer component. Each polymer component may contain oneor more types of thermoplastic polymers.

[0025] Other materials may also be utilized in conjunction with thethermoplastic polymer(s) to form the thermoplastic tape of the presentinvention. For example, in some embodiments, various materials can becoated onto one or more surfaces of the tape and/or along the edges ofthe tape to enhance the ability of the tape to bond to one or moresubstrates. Some examples of additional materials that can be utilizedin conjunction with a thermoplastic polymer include, but are not limitedto, solvent-based adhesives, discrete raised beads of an adhesivematerial, etc.

[0026] In some embodiments, the tape may be utilized in a flatconfiguration, while in other embodiments, the tape may be utilized in afolded or shaped configuration. For example, referring to FIGS. 2-3, oneembodiment of the present invention is illustrated in which athermoplastic tape 10 is shown folded in a “z-shaped configuration” toform a first section 16, a second section 17, and a third section 18.The sections 16, 17, and 18 may be a single continuous strip or two ormore separate strips. When formed from separate strips, such strips maybe unattached (e.g., two or more U-shaped sections) or attached usingconventional techniques. Moreover, the separate strips, when utilized,may be formed from the same or different materials. It should beunderstood that the tape 10 need not possess three sections, but canpossess any number of sections desired.

[0027] Regardless of the particular method used to construct thesection(s), in the embodiment of the z-shaped configuration illustratedin FIG. 3, the lower surface 36 of the first section 16 faces the uppersurface 27 of the second section 17, while the lower surface 37 of thesecond section 17 faces the upper surface 28 of the third section 18.The tape 10 may generally be shaped or folded, such as described above,using a variety of different techniques. For example, in someembodiments, a thermoplastic material can be extruded onto a formingsurface that has the shape of the desired fold. Thus, as the polymer isdeposited onto the forming surface, it naturally assumes the shape ofthe forming surface. In other embodiments, the thermoplastic materialcan be extruded as a flat ribbon and then folded through the use of aseries of guide bars. Once folded, light heat and pressure can beapplied to set the folded shape.

[0028] In accordance with the present invention, once the particularthermoplastic tape and substrates are provided, they are then placedinto operative communication such that the tape can form a seam betweenthe substrates. In this regard, various embodiments for placing thethermoplastic tape into operative communication with the substrates toform a seam will now be described in more detail. It should beunderstood, however, that the embodiments discussed below are onlyintended to illustrate some examples of the present invention, and thatother embodiments and techniques for placing a thermoplastic tape intooperative communication with one or more substrates are alsocontemplated by the present invention.

[0029] For example, referring to FIG. 3, one embodiment of a method offorming a seam between two substrates and a tape folded in a z-shapedconfiguration is illustrated. As shown, a first substrate 11 ispositioned between the lower surface 36 of the first section 16 of thetape 10 and the upper surface 27 of the second section 17 of the tape10. In addition, the second substrate 14 is positioned between the lowersurface 37 of the second section 17 of the tape 10 and the upper surface28 of the third section 18 of the tape 10. In most embodiments, thesubstrates are positioned such that the edges 64 and 62 are in anoverlapped position, such as shown in FIG. 3. As a result, the tape 10can be more readily placed into contact with the upper and lowersurfaces of each of the substrates 11 and 14.

[0030] In some embodiments, the tape 10 may also be placed intooperative communication with the substrates 11 and 14 before the tape 10is shaped or folded. For example, in one embodiment of the presentinvention, a flat thermoplastic tape 10 (See FIG. 1) is placed incommunication with two substrates 11 and 14 by overlapping the tape 10over certain portions of the substrates 11 and 14. Thereafter, heat andpressure can be applied to lightly bond the flat tape 10 to thesubstrates 11 and 14. Once lightly bonded, a series of guide bars canthen be utilized to shape or fold the tape 10 as desired.

[0031] After the substrates 11 and 14 have been placed in communicationwith the tape 10, such as described above, they can then be supplied toa conventional seam assembly device (not shown) where heat and pressureare applied to seal the materials and form the desired seam. Althoughnot required, heat and pressure are typically applied simultaneously. Ingeneral, any of a variety of conventional methods for applying heat andpressure to a material can be utilized in the present invention. Forinstance, some examples of suitable methods for applying heat andpressure include, but are not limited to, the use of heated nip rolls,hot calendering techniques, ultrasonic welding techniques, the use oflasers in conjunction with nip rolls, the use of certain radiofrequencies in conjunction with nip rolls, combinations thereof, and thelike.

[0032] The particular pressure and temperature utilized can varydepending on a variety of factors, such as the materials utilized forthe tape and/or substrate(s), the size and shape of the tape and/orsubstrate(s), the desired seam width, the desired strength of the seam,the type of seam construction, etc. For example, in most instances, theseam can be formed at a temperature that ranges from about 10° C. lessthan the thermal melting temperature of the thermoplastic material ofthe tape 10 having the lowest thermal melting temperature, up to atemperature of about 50° C. above such thermal melting temperature. Forexample, in one embodiment, a bilayer polyurethane tape having a thermalmelting point of 147° C. can be heated at a processing temperature ofbetween about 170° C. to about 195° C. In addition, the seam can beformed at a processing pressure between about 40 pounds per square inchto about 120 pounds per square inch. Thus, in the embodiment shown inFIG. 3, pressure can be applied to compress the z-shaped configurationof the tape 10 by applying a compressive force to the first section 16and/or the third section 18. In one embodiment, for instance, thematerials can be hand pressed at a temperature of about 110° C. forabout 5 seconds. In another embodiment, the materials can be handpressed at a temperature of between about 170° C. to about 195° C. for10 seconds.

[0033] Once heat and pressure have been applied, the tape 10 can form aseam with the substrates 11 and 14. As described above, the seam canhave any of a variety of configurations and constructions. For example,referring to FIG. 4, one embodiment of a seam 70 is shown in which theseam 70 is defined by the region of the tape 10 positioned between thesubstrates 11 and 14.

[0034] In accordance with the present invention, it has been discoveredthat the seam formed between the thermoplastic tape and the substratesutilizes both “adhesive bonds” and “physical bonds” to enhance thestrength of the seam. An “adhesive bond” generally refers to a bond thatresults from attractive forces between two or more materials. Forinstance, adhesive bonds may sometimes result from “dipole-dipoleforces” between materials, which are a type of van der Waals force thatoccurs upon the interaction of the dipole moments of two polarmolecules.

[0035] Besides forming an adhesive bond with the substrates, however, ithas also been discovered that the thermoplastic tape can also form a“physical bond”. For example, in one embodiment, after being heated to acertain temperature, at least a portion of the first section 16 and/orthe second section 17 of the tape 10 can be softened or melted such thatthe portion becomes relatively melt-flowable. Moreover, upon beingsubjected to a certain pressure, the polymer of such melt-flowableportions of the tape 10 can be forced between the interstices of thetopography of the substrates 11 and 14. Thereafter, the seam is allowedto cool, whereby the melt-flowable portions solidify within theinterstices of the substrates 11 and 14 to form a contiguous “physicalbond” therewith. For example, referring to FIGS. 6A-6B, certainmelt-flowable portions 88 of a polyurethane bilayer tape 10 are shown inphysical contact with two substrates 11 and 14.

[0036] Thus, because the tape is capable of forming adhesive andphysical bonds with one or more substrates, the strength of theresulting seam can be significantly enhanced. In particular, it has beendiscovered that seams formed according to the present invention canattach substrates without the use of conventional needle stitching, butcan nevertheless possess a strength that approximates the strengthobtained using conventional stitching. However, it should be understoodthat conventional stitching may be used in conjunction with the seam ofthe present invention if desired.

[0037] Moreover, it should also be understood that, in some instances,the tape 10 may only form a small amount of physical or adhesive bondswith a particular substrate. In particular, one unique aspect of thepresent invention is the ability to form a seam between materials thatmay not readily able to form adhesive or physical bonds with thethermoplastic tape. In such instances, it may be desired to controlcertain aspects of seam formation in order to better control the extentof adhesive bonding and/or physical bonding.

[0038] For example, in some embodiments, the processing temperaturesand/or pressures can be selected to favor certain types of bonding. Forinstance, a lower processing temperature can be utilized to produce aseam that is bonded to the substrates 11 and 14 primarily throughadhesive bonding. Specifically, at lower processing temperatures, asmaller amount of the thermoplastic polymer(s) used in forming the tape10 will become melt-flowable. As a result, the tape 10 physically bondsto the substrates 11 and 14 to a lesser extent. On the other hand, athigher processing temperatures, a greater amount of the thermoplasticpolymer(s) used in forming the tape 10 will become melt-flowable,thereby increasing the extent of physical bonding between the tape 10and the substrates 11 and 14.

[0039] In addition, besides varying the processing conditions, theparticular tape and/or substrate construction can also affect the natureof bonding between the tape 10 and the substrates 11 and 14. Forexample, in certain embodiments, the substrates 11 and/or 14 may beformed from a non-fibrous or non-porous material, such as a butyl rubbersheet. In such instances, it may be desired to increase the surface areaof the substrate to facilitate physical bonding therewith. For example,the edge of the substrate can be cut in a non-linear pattern to increaseits surface area. Such non-linear patterns can be provided by a“pinking” saw-tooth shear cut or patterns created by a knife or diecutter (e.g., ultrasonic die cutter). Furthermore, etching (e.g., plasmaetching) can be utilized to create a three-dimensional topography on oneor more surfaces of a substrate. Such a three-dimensional topography canprovide an “anchor” for the melt-flowable polymer during processing toenhance physical bonding of the tape to the substrate.

[0040] In addition to varying the construction of the substrate(s), theconstruction of the thermoplastic tape may also be varied to control theextent of adhesive and physical bonding. For instance, in someembodiments, a multi-layer thermoplastic tape (e.g., two layers, threelayers, etc.) can be utilized to vary the extent of adhesive andphysical bonding. Referring to FIG. 5, for example, one embodiment atwo-layer thermoplastic tape 10 is shown in which a first layer 40 formsthe upper surface 26 of the first section 16 of the tape 10 and a secondlayer 50 forms the lower surface 36 of the first section 16 of the tape10.

[0041] To alter the extent of adhesive and physical bonding, thematerials used in forming the layers 40 and 50 can be preselected toresult in a certain type of bond. For example, in one embodiment, thelayer 40 can be formed from a first material that has a certain meltingpoint, while the layer 50 can be formed from a second material that hasa melting point that is greater than the melting point of the firstmaterial. Thus, certain portions of the tape 10 can bond to a substrateprimarily through adhesive bonding, while other portions of the tape 10can bond to a substrate primarily through physical bonding.Specifically, in this embodiment, the lower surface 36 of the firstsection 16 and the upper surface 27 of the second section 17 can bond tothe substrate 11 primarily through adhesive bonding, while the lowersurface 37 of the second section 17 and the upper surface 28 of thethird section 18 can bond to the substrate 14 primarily through physicalbonding.

[0042] Such preferential bonding can be particularly useful when thematerials that form the substrate 11 differ from the materials that formthe substrate 14. For instance, in some embodiments, the substrate 14may be relatively “adhesively” incompatible with the tape 10. Moreover,in other embodiments, the substrate 11 may have a thermal melting pointthat is relatively incompatible with the thermal melting point of thetape 10. Nevertheless, because the tape 10 is capable of adhesive andphysical bonding, it can still form bonds having excellent strength withboth the substrates 11 and 14.

[0043] In addition to being able to form a strong seam between twosubstrates, the thermoplastic tape used in the present invention canalso protect one or more edges of the substrates. In particular, asshown in FIG. 3, the tape 10 can substantially cover the edge 62 of thesubstrate 11 and the edge 64 of substrate 14 so that, upon theapplication of heat and pressure, the tape 10 forms a seal over theedges 62 and 64. This seal can prevent various objects from abrading orpicking at the edges of the substrates, which could eventually lead tothe degradation of the bond between the substrates.

[0044] The present invention may be better understood with reference tothe following examples.

EXAMPLE 1

[0045] The ability of two substrates to be joined with a thermoplastictape in accordance with one embodiment of the present invention wasdemonstrated. Two substrates were obtained from the U.S. Army SoldierSystems Center in Natick, Mass. The substrates were prepared from asheet material specified by Military Specification MIL-C-13621.Specifically, the sheet contained three layers and had an overall basisweight of between 370 to 460 grams per square meter (gsm). The innerlayer was a scrim of nylon fabric having a twill weave. In addition, theouter layers were formed from butyl rubber. The edges of the substrateswere cut with pinking shears prior to fabricating the seam.

[0046] The thermoplastic tape utilized was a modified polyurethanetwo-layer film available under the name ST-52 from Bemis Associates,Inc. of Shirley, Mass. In particular, one layer contained a polyurethaneadhesive and had a thickness of 0.064 millimeters, while the other layercontained a polyurethane barrier material and had a thickness of 0.101millimeters. The melting temperature of the adhesive layer was 82° C.and the melting temperature of the barrier layer was 147° C. The tapehad a width of 22.2 millimeters.

[0047] To form the seam, the thermoplastic tape was initially placedinto communication with the substrates to form a seam gauge, which wasdefined by an overlap of 6.35 mm of the fabric edges. The tails of thetape extended 1.6 mm beyond the fabric edges on the upper and lowersurfaces of the seam. One edge of the thermoplastic tape waspre-attached to the edge of one of the fabric pieces using a SonobondModel SM8000 Ultrasonic Sewing Machine, available from SonobondUltrasonics of West Chester, Pa. The sewing machine was set with a hornheight of 2.3 millimeters, an amplitude setting of 1.5, and a residencetime of 1 second. Tack points were set approximately 6 mm apart.

[0048] The second fabric piece was pre-attached to the thermoplastictape in a similar manner. The tape was then folded to place the fabricedges in an overlapping position, such as shown in FIG. 4. A flat buckpress was then used to bond the materials. In particular, the press wasutilized at temperatures of 170° C. and 195° C., a pressure of about 5.6kg/cm², and for a residence time of about 10 seconds.

EXAMPLE 2

[0049] The ability of two substrates to be joined with a thermoplastictape in accordance with one embodiment of the present invention wasdemonstrated. Two substrates were obtained from the U.S. Army SoldierSystems Center in Natick, Mass. The substrates were prepared from a tentshelter fabric as described in Military Specification MIL-PRF-44103D,Class 2, Grade B. Specifically, the fabric was a coated, woven nylonwith a desert tan camouflage print.

[0050] The thermoplastic tape utilized was a modified polyurethanetwo-layer film available under the name ST-52 from Bemis Associates,Inc. of Shirley, Mass. In particular, one layer contained a polyurethaneadhesive and had a thickness of 0.064 millimeters, while the other layercontained a polyurethane barrier material and had a thickness of 0.101millimeters. The melting temperature of the adhesive layer was 82° C.and the melting temperature of the barrier layer was 147° C. The tapehad a width of 22.2 millimeters.

[0051] The seam was formed as described in Example 1. In addition, theGrab Tensile Strength of three samples of the fabric and seam weretested according to ASTM D-5034. The fabric failed at loads of 155 to160 kg. The average Grab Tensile Strength of the three seam tests was150.98 kg.

EXAMPLE 3

[0052] Example 3 was prepared according to Example 2, except that theseam gauge was 3.175 millimeters and the thermoplastic tape had a widthof 19 millimeters. Three sample seams were again tested for Grab TensileStrength. For one of the seams, the fabric failed before the seam, i.e.,at a load of 157.4 kg. The other two seams failed at loads of 134.3 kgand 136.3 kg.

EXAMPLE 4

[0053] The ability of two substrates to be joined with a thermoplastictape in accordance with one embodiment of the present invention wasdemonstrated. Two substrates were obtained from the U.S. Army SoldierSystems Center in Natick, Mass. The substrates were prepared from athree-layer fabric as described in Military Specification MIL-C-44187.Specifically, this fabric was constructed of a plain weave nylon fabrichaving a basis weight between 88 to 102 grams per square meter (gsm),laminated to a polytetrafluoroethylene (PTFE) microporous film having abasis weight of between 10 to 24 gsm. The backing of the fabric was anylon tricot knit fabric backing having a basis weight of between 34 to62 gsm.

[0054] The thermoplastic tape utilized was a tape formed from threeseparate strips of a modified polyurethane two-layer film availableunder the name ST-52 from Bemis Associates, Inc. of Shirley, Mass. Inparticular, one layer contained a polyurethane adhesive and had athickness of 0.064 millimeters, while the other layer contained apolyurethane barrier material and had a thickness of 0.101 millimeters.The melting temperature of the adhesive layer was 82° C. and the meltingtemperature of the barrier layer was 147° C. The resulting tape had awidth of 7 millimeters.

[0055] The seam was formed and as described in Example 2. The GrabTensile and Peel Strength of the fabric and the seam were testedaccording to ASTM D-5034 and ASTM D-2724 (sections 14-15), respectively.The average Grab Tensile Strength of the three seam tests was 114 kg andthe average Grab Peel Strength for these seams was 2.28 kg.

EXAMPLE 5

[0056] For purposes of comparison, a conventional lap seam having a seamgauge of 6.3 millimeters was utilized to attach the two substratesdescribed in Example 4. After sewing the seam through the substrates,two strips of thermoplastic tape were also utilized. In particular, onestrip of thermoplastic tape was placed in its entirety only on the uppersurface of one substrate to adhere one end of the seam thereto. Theother strip was placed in its entirety only on the lower surface of theother substrate to adhere the other end the sewn seam thereto. Thestrips of tape were then heated and pressed to set the tape.

[0057] The average Grab Tensile of these seams was 78 kg and the averagePeel Strength of these seams was 1.53 kg.

EXAMPLE 6

[0058] For purposes of comparison, a conventional double-felled needlesewn seam was utilized to attach the two substrates described in Example4. The average Grab Tensile of these seams was 85.1 kg and the averagePeel Strength of these seams was 4.03 kg.

[0059] A summary of the results obtained in Examples 2 through 6 isprovided below in Table I. TABLE I Summary of Examples Avg. Seam GrabAvg. Seam Peel Ex.# Substrate Seam Tensile (kg) Strength (kg) 2 CoatedWoven -z fold 150.98 — Nylon 3 Coated Woven -z fold 135.3 — Nylon 4Three-layer -z fold 114 2.28 5 Three-layer Lap 78 1.53 6 Three-layerDouble 85.1 4.03 needle

[0060] Thus, as shown from Table I, a seam formed according to thepresent invention can provide enhanced bonding strength in comparison toseams formed according to conventional techniques. In particular, theability of the thermoplastic tape to form physical and adhesive bondscan provide a seam of unexpected strength and durability. Such seams canbe utilized in a wide variety of applications. For example, the seamsmay be useful in joining barrier materials, particularly when thebarrier function must be maintained in the seam area. Examples of suchbarrier materials include protective apparel for biological exposureareas, chemical warfare, and underwater diving suits. Further, becausethe seams of the present invention do not rely upon needle stitching,they may have enhanced utility in applications requiring controlled airporosity, such as in parachute constructions. Moreover, otherapplications in which the seams may be useful include tents, militaryuniforms, fabric-covered air ships (e.g., blimps), and the like.

[0061] These and other modifications and variations of the presentinvention may be practiced by those of ordinary skill in the art,without departing from the spirit and scope of the present invention,which is set forth in the appended claims. In addition, it should beunderstood that aspects of the various embodiments may be interchangedboth in whole or in part. Furthermore, those of ordinary skill in theart will appreciate that the foregoing description is by way of exampleonly, and is not intended to limit the invention so further described insuch appended claims.

What is claimed is:
 1. A method of forming a seam between substratescomprising: providing a first substrate having an upper surface and alower surface, said upper and said lower surfaces of said firstsubstrate defining at least one edge; providing a second substratehaving an upper surface and a lower surface, said upper and said lowersurfaces of said second substrate defining at least one edge;overlapping said edge of said first substrate with said edge of saidsecond substrate; positioning a first tape portion adjacent to saidfirst substrate such that said first tape portion is placed in operativecommunication with said upper and said lower surfaces of said firstsubstrate, said first tape portion comprising a thermoplastic materialthat is melt-flowable when subjected to a certain amount of heat andpressure; positioning a second tape portion adjacent to said secondsubstrate such that said second tape portion is placed in operativecommunication with said upper and lower surfaces of said secondsubstrate, said second tape portion comprising a thermoplastic materialthat is melt-flowable when subjected to a certain amount of heat andpressure; forming an adhesive bond and a physical bond between saidfirst tape portion and said first substrate and between said second tapeportion said second substrate.
 2. A method as defined in claim 1,wherein said first tape portion and said second tape portion areattached together.
 3. A method as defined in claim 1, wherein said firsttape portion and said second tape portion are continuous.
 4. A method asdefined in claim 1, wherein said first tape portion and said second tapeportion are unattached.
 5. A method as defined in claim 1, furthercomprising heating said first tape portion to a first predeterminedtemperature.
 6. A method as defined in claim 5, wherein said firstpredetermined temperature is between about 10° C. below the thermalmelting temperature of said thermoplastic material to about 50° C. abovethe thermal melting temperature of said thermoplastic material.
 7. Amethod as defined in claim 1, further comprising heating said secondtape portion to a second predetermined temperature.
 8. A method asdefined in claim 7, wherein said second predetermined temperature isbetween about 10° C. below the thermal melting temperature of saidthermoplastic material to about 50° C. above the thermal meltingtemperature of said thermoplastic material.
 9. A method as defined inclaim 1, further comprising subjecting said first tape portion and saidsecond tape portion to pressure.
 10. A method as defined in claim 9,wherein said pressure is between about 40 pounds per square inch toabout 120 pounds per square inch.
 11. A method as defined in claim 1,further comprising subjecting said first tape portion to simultaneousheat and pressure and subjecting said second tape portion tosimultaneous heat and pressure.
 12. A method as defined in claim 1,wherein said first substrate and said second substrates are fabrics. 13.A method as defined in claim 1, wherein at least one of said tapeportions contains multiple layers.
 14. A method as defined in claim 12,wherein one of said layers contains a thermoplastic material having afirst thermal melting temperature and another of said layers contains athermoplastic material having a second thermal melting temperature, saidsecond thermal melting temperature being greater than said first thermalmelting temperature.
 15. A method as defined in claim 1, furthercomprising folding said tape portions into a certain shape.
 16. A methodas defined in claim 15, wherein said tape portions are folded into az-shaped configuration.
 17. A method as defined in claim 15, whereinsaid tape portions are folded prior to being placed adjacent to saidfirst substrate and said second substrate.
 18. A method as defined inclaim 15, wherein said tape portions are folded after being placedadjacent to said first substrate and said second substrate.
 19. A methodas defined in claim 1, further comprising imparting a three-dimensionaltopography on at least one of said surfaces of said first substrate. 20.A method as defined in claim 1, further comprising imparting athree-dimensional topography on at least one of said surfaces of saidsecond substrate.
 21. A method as defined in claim 1, wherein said edgeof at least one of said substrates is non-linear.
 22. A method offorming a seam between substrates comprising: providing a firstsubstrate having an upper surface and a lower surface, said upper andsaid lower surfaces of said first substrate defining at least one edge;providing a second substrate having an upper surface and a lowersurface, said upper and said lower surfaces of said second substratedefining at least one edge; overlapping said edge of said firstsubstrate with said edge of said second substrate; positioning a firsttape portion adjacent to said first substrate such that said first tapeportion is placed in operative communication with said upper and saidlower surfaces of said first substrate, said first tape portioncomprising a thermoplastic material that is melt-flowable when subjectedto a certain amount of heat and pressure; positioning a second tapeportion adjacent to said second substrate such that said second tapeportion is placed in operative communication with said upper and lowersurfaces of said second substrate, said second tape portion comprising athermoplastic material that is melt-flowable when subjected to a certainamount of heat and pressure; folding said tape into a z-shapedconfiguration; subjecting said first tape portion to simultaneous heatand pressure; subjecting said second tape portion to simultaneous heatand pressure; and forming an adhesive bond and a physical bond betweensaid first tape portion and said first substrate and between said secondtape portion said second substrate.
 23. A method as defined in claim 22,wherein said tape portions are folded prior to being placed adjacent tosaid first substrate and said second substrate.
 24. A method as definedin claim 22, wherein said tape portions are folded after being placedadjacent to said first substrate and said second substrate.
 25. A methodas defined in claim 22, wherein said first substrate and said secondsubstrates are fabrics.
 26. A method as defined in claim 22, furthercomprising imparting a three-dimensional topography on at least one ofsaid surfaces of said first substrate.
 27. A method as defined in claim22, further comprising imparting a three-dimensional topography on atleast one of said surfaces of said second substrate.
 28. A method asdefined in claim 22, wherein said edge of at least one of saidsubstrates is non-linear.
 29. A seam for joining two or more substratesof an article, said seam comprising: a first substrate having an uppersurface and a lower surface, said upper and said lower surfaces of saidfirst substrate defining at least one edge; a second substrate having anupper surface and a lower surface, said upper and said lower surfaces ofsaid second substrate defining at least one edge, said edge of saidsecond substrate overlapping said edge of said first substrate; a firsttape portion comprising a thermoplastic material that is melt-flowablewhen subjected to a certain amount of heat and pressure, said first tapeportion being adhesively and physically bonded to said upper and saidlower surfaces of said first substrate; a second tape portion comprisinga thermoplastic material that is melt-flowable when subjected to acertain amount of heat and pressure, said second tape portion beingadhesively and physically bonded to said upper and said lower surfacesof said second substrate.
 30. A seam as defined in claim 29, whereinsaid first and said second substrates are fabrics.
 31. A seam as definedin claim 29, wherein said edge of at least one of said substrates isnon-linear.
 32. A seam as defined claim 29, wherein at least one of saidsurfaces of said first substrate has a three-dimensional topography. 33.A seam as defined claim 29, wherein at least one of said surfaces ofsaid second substrate has a three-dimensional topography.
 34. A seam asdefined in claim 29, wherein at least one of said tape portionscomprises polyurethane.
 35. A seam as defined in claim 29, wherein atleast one of said tape portions contains multiple layers.
 36. A seam asdefined in claim 35, wherein one of said layers contains a thermoplasticmaterial having a first thermal melting temperature and another of saidlayers contains a thermoplastic material having a second thermal meltingtemperature, said second thermal melting temperature being greater thansaid first thermal melting temperature.
 37. A seam as defined in claim29, wherein said tape portions form a z-shaped configuration.
 38. A seamas defined in claim 29, wherein said first tape portion and said secondtape portion are attached together.
 39. A seam as defined in claim 29,wherein said first tape portion and said second tape portion arecontinuous.
 40. A seam as defined in claim 29, wherein said first tapeportion and said second tape portion are unattached.